Coronary microvascular dysfunction in postmenopausal minipigs with cardiovascular kidney-metabolic syndrome

Background - Coronary microvascular angina is most prevalent in postmenopausal women with multiple cardiovascular risk factors, contributing to the development of cardiovascular–kidney–metabolic syndrome, (CKM). The absence of effective treatments for coronary microvascular dysfunction highlights the need to elucidate its underlying mechanisms in this expanding patient group. Here we studied microvascular function and structure in vivo and and in vitro, in post-menopausal miniswine with CKM. Methods Diabetes, (streptozotocin), hypercholesterolemia (high fat, high sugar, high salt diet), chronic kidney dysfunction (renal artery embolization) and menopause (ovariectomy) were induced in 5 adult female minipigs (1.5-2 years old, ~40kg, CKM) for 6 months, while 11 healthy age- and weight-matched female minipigs on normal pig chow served as controls (Normal). At sacrifice, coronary flow reserve (CFR, adenosine i.c.) was measured under anesthesia. Isolated small coronary arteries were used to study the endothelium-dependent response to bradykinin and endothelium-independent response to the nitric oxide donor, SNAP. The contributions of nitric oxide, (NO) and prostacyclins to bradykinin-induced dilation were tested after eNOS and cyclo-oxygenase inhibition. Structure of the large and small coronary arteries was studied using histology. Results Sustained hyperglycemia (17.5±1.0 in CKM vs 8.2±0.9 mmol/l in Normal, P<0.05 by t-test), hypercholesterolemia (15.4±2.0 vs 1.7±0.1 mmol/l, P<0.05), renal dysfunction (GFR; 51±10 vs 86±3 mL/min/1.73 m², P<0.05) and low progesterone levels (13.1±5.7 vs 92.0±030.0 nmol/l, P=0.1) were accompanied by systemic inflammation (TNFα: 62±7 vs 47±1 pg/ml, P<0.05). CFR was significantly reduced in CKM vs the healthy animals (panel A). Coronary small arteries from CKM animals showed impaired endothelium-dependent vasodilation to bradykinin (panel B), mediated by a loss of NO (panels C & D), which was partly compensated for by activation of the cyclo-oxygenase, as indomethacin blunted the dilation to bradykinin only in the CKM animals (panels C & D). Endothelium-independent dilation to SNAP was also impaired in CKM, indicating blunted vascular smooth muscle responsiveness to nitric oxide (panel E). Additionally, CKM animals exhibited increased medial thickness of the large coronary arteries and enhanced perivascular collagen deposition around small coronary arterioles (<50µm diameter). Conclusion Postmenopausal minipigs with CKM exhibited modest coronary vascular structural alterations but pronounced microvascular dysfunction as evidenced by a significantly reduced coronary flow reserve and reduced NO sensitivity/ production, indicating endothelial and smooth muscle cell dysfunction. Partial compensation occurred via activation of cyclo-oxygenase pathway. Such perturbations may contribute to reduced myocardial perfusion that is often observed in post-menopausal women with multiple cardiovascular risk factors.